Frequently Asked Questions

I am renovating my house. What are the advantages of using lime-based mortars?

Lime mortars are less dense and more vapour permeable. They therefore do not trap water in your walls. Trapped water is one of the principal agents of decay in all buildings. Lime mortars are also closer in strength to many types of stone and brick and therefore do not exaggerate their decay like cement based mortars often do.

Can I apply a lime plaster to plasterboards?

It is very difficult to successfully apply lime plaster to plasterboards and offers no real advantages for the building. If you want to avoid applying a very dense sterile modern gypsum skim coat on top of boards you could use our textured natural plasters, these will add character and depth to your walls and ceilings.

If you wish to have a lime finish on boards, for instant on a ceiling, to avoid having to put up a new lath and plaster ceiling, you can use clay plasterboards.

Somebody told me that I should only use slaked none hydraulic lime mortars. Is this true?

No there is full range of lime mortars with different strengths and degrees of resistance to damp conditions. You should choose the right one, bearing in mind the exposure of the wall, the location of the property and the condition of the stone or brickwork that you are repairing, rendering or re-pointing. If you require specific free advice on appropriate mixes please contact us or read our technical sheets.

If I use lime mortar will it cure damp problems in my house?

Lime mortar will not cure a problem caused by poor detailing on the property, such as undersized gutters, a lack of a roof overhang, outside ground levels that are higher than floor levels or capped unventilated chimney stacks. They will however allow walls to dry out after problems such as this have built up high damp levels within walls and they will allow the wall to be able to breathe again.

How high can I build with lime mortar before I have to wait for it to set?

Fat lime mortars require construction to take place at a slower rate but hydraulic limes cure quickly enough to allow building work to proceed quickly and do not delay work even on the largest construction sites.

What are the advantages of using a lime render rather than cement render?

Even the British Cement Association in their publication 'External Appearance Matters' recognise that it is inappropriate to use a hard cement based render on most backgrounds because they trap water behind the render within the wall. The simple advantage of using a lime render is that they allow walls to breathe-out any water that penetrates into them. In addition, lime renders do not put the same stresses and strains on older more fragile building materials. These often require the use of stainless steel mesh when cement based render is used.

Can I use lime renders as part of insulated render system?

Yes lime renders can be combined with external, wood fibre insulation boards to create insulated breathable render systems. See technical sheets for more details.

What mortar mix should I use for pointing?

You should choose a mortar that is more vapour permeable and less dense that the stone or brickwork into which is being put to ensure that it reduces the decay of this stone or brick as much as possible.

If I use sheep’s wool insulation will the damp damage it and won’t insects want to live in it?

The sheep’s wool insulation that we supply is treated with natural materials that prevent it from degrading or being damaged by pests or fungal attack. It also resists damp exceptionally well. It works on the sheep and it works in your buildings.

Why do people use lime and clay plasters?

People use lime plasters inside to replicate the finish that is found in our historic buildings but also on the internal face of external solid walls because they allow these walls to breathe moisture out of them.

Clay plasters have the added advantage of being able to control the relative humidity of our internal environments and create healthier living conditions.

Why shouldn’t I use modern building materials in an old building?

There are some excellent well thought out modern building materials and there are excellent tried and tested traditional materials, you should use the best of the old and the best of the new. However, please do not try and combine them without advice. For instance, it is inappropriate to try and hang a fat lime plaster off stainless steel mesh.

Which paint should I use on old walls?

Old walls especially the external ones need to be able to breathe. Try and pick the most vapour permeable paint that is hard wearing enough for the location of the wall. Lime washes, washable casein distempers and silicate paints are the most vapour permeable, natural resin walls paints are also very good but please try and avoid using dense film forming paints.

What is natural paint?

A natural paint is one that is only made from natural organic based materials and not petrochemical derivatives.

If normal paints are so bad for us, why do we still use them and why hasn’t the government banned them?

Legislation and advice has been issued which restricts the amount of dangerous volatile organic gases which paints can now contain but like many things there is a time lag even when harm has been proven, especially because of the power of political lobbyists.

Aren’t all natural products more expensive and more difficult to use?

No, many natural less toxic materials are no more difficult to use than conventional alternatives. Some are more expensive but some are cheaper. All are cheaper in the long term if you take into account the impact of the manufacture, use and disposal.